It is known that strength and hardness of metallic alloys may be enhanced by dispersions of small amounts of a second phase of metal or of metal oxide additives. For example, it is known that copper may be hardened and strengthened by the addition of cobalt. Similarly, among well-known examples of oxygen containing, dispersion strengthened alloys are Cu-Al and Cu-Si alloys in which Cu is a primary, less easily oxidized component and Al or Si a more easily oxidized additive.
The incorporation of oxides in alloys may be effected by a variety of procedures such as, e.g., by direct reduction, by powder metallurgy, or by internal oxidation. The latter, most recently disclosed process generally calls for the preparation of a body of an alloy containing desired metallic constituents, followed by selective internal oxidation of a more easily oxidized component by oxygen diffusion.
Specific internally oxidized alloys are disclosed in U.S. Pat. No. 3,184,835, issued May 25, 1965 to Charles D. Coxe et al. which discloses single phase alloys consisting of copper as a primary, solvent constituent and beryllium oxide or aluminum oxide as a solute, secondary constituent. Also disclosed are silver alloys in which silver is a solvent and magnesium oxide or aluminum oxide a solute constituent.
In contrast to single phase alloys disclosed by Coxe et al., two-phase oxidation hardened alloys are disclosed in U.S. Pat. No. 3,922,180, issued Nov. 25, 1975 to E. O. Fuchs et al. Particularly disclosed are, e.g., copper, silver, and gold two-phase alloys containing oxides of easily oxidizable metals such as, e.g., Zr, Hf, rare earths, and actinides. Two-phase alloys may be prepared, e.g., from a melt containing an easily oxidizable metal by casting and quenching, by working a solidified body, or by a combination of quenching and working. Internal oxidation of the easily oxidizable component may be effected by heating the resulting body in an oxygen atmosphere. As compared with single phase alloys, oxidation hardened two-phase alloys have superior electrical conductivity; consequently, these alloys are particularly suited for the manufacture of articles such as, e.g., electrical wire, switch contacts, and relay elements. Still, in view of relatively slow, substitutional diffusion of oxygen, there arises a desire for methods which permit reaching desired levels of strength and hardness in shorter time. Moreover, means are desired for strengthening and hardening metal alloys at temperatures more easily reached by heating facilities in commercial use.